Durability and Steel Corrosion Resistance of Fly Ash Concrete Exposed to Groundwater

This article proposes replacing Ordinary Portland Cement (OPC) with a fly ash (FA)-based geopolymer (GP) material, activated by a chemical activator, as the binding material. A 90-day study was conducted to evaluate the performance of fly ash geopolymer concrete (GPC) in a corrosive environment (groundwater). Scanning electron microscopy (SEM), compression testing, and energy-dispersive X-ray spectroscopy (EDX) were used to assess the toughness of the samples. Additionally, the linear polarization resistance (LPR) method was employed to measure the corrosion of steel embedded in the concrete structures. The comparison shows that increasing the fly ash (FA) content in geopolymer concrete (GPC) enhances its performance. Moreover, FA-based GPC exhibits superior strength compared to ordinary Portland cement (OPC) concrete. The results indicate that the compressive strengths of the geopolymer samples FA 400, FA 450, and FA 500 were higher than that of the OPC sample by approximately 32.2%, 48.8%, and 69.83%, respectively. Furthermore, the compressive strength of GPC under severe attack conditions was about 2.5 times higher than that in tap water. In addition, the GP model demonstrated a significantly lower corrosion rate for the steel compared to the OPC model, approximately 300 times lower. Compared to OPC, the microstructure of the GP matrix exhibited more stable behavior under severe conditions. Microstructural analysis revealed that GPC maintained a stable mineral composition after exposure to harsh conditions, unlike OPC